Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$247.33	6.781%	$264.1014	$264.10	$264.10	$264.10
Purchase #2	$156.61	5.837%	$165.7513	$165.75	$165.75	$165.80
Purchase #3	$141.70	6.506%	$150.919	$150.92	$150.90	$150.90
Purchase #4	$222.99	11.651%	$248.9706	$248.97	$248.95	$249.00
Purchase #5	$53.56	3.195%	$55.2712	$55.27	$55.25	$55.30
Purchase #6	$135.65	11.134%	$150.7533	$150.75	$150.75	$150.80
Purchase #7	$139.93	9.709%	$153.5158	$153.52	$153.50	$153.50
7 purchase totals =	$1,097.77		$1,189.2826	$1,189.28	$1,189.20	$1,189.40